Current telephone systems in the United States and Canada use the North American Number Plan (NANP) for establishing calls. Under the NANP, NPA.NXX identifiers are used. NPA.NXX refers to the first six digits in a phone number. NPA refers to the area code, and NXX refers to the exchange (three digits following the area code). Service providers use the NPA.NXX identifiers of each party (called party and calling party) to determine the rates to be charged for a call. Also, persons with caller ID have used the NPA.NXX identifiers to determine the origination of a call. However, with the widespread use of portable communications devices, such as cellular phones, VoIP, and local number portability features available in wireline systems (e.g., landline systems), the NPA.NXX identifiers may not accurately reflect the location of a party.